Fractal DNA
A three-dimensional model of human DNA is presented for the first timemembrana
Scientists from several US universities worked on the creation of a three-dimensional model of the human genome.
Their work will allow us to better study the functions of the double helix and how it acquires its unusually compressed form inside the cell nucleus.
"Everyone knows that DNA is a double helix. But how does this almost two-meter chain fit into the core, whose diameter is hundredths of a millimeter? Even scientists have not fully figured it out. We started to clarify this issue," says Erez Lieberman–Aiden from Harvard.
To achieve such an impressive result, the geneticists were helped by the method they developed, which they themselves call Hi-C. Thanks to this technology, scientists were able to study the position of all genes, even those that are very close to each other.
"We broke the genome into many pieces, created a spatial map showing how close the individual parts are to each other. Then, with the help of a computer, they put everything together," says one of the Harvard researchers, Nynke van Berkum, in a press release.
In these images, close sections of DNA are colored with the same color.
It is clearly seen that in the equilibrium globule (above), parts of the genome are mixed up in three-dimensional space,
and in the fractal globule (below) with its hierarchical structure, they are located close to each other in volume
(illustration by Leonid A. Mirny, Maxim Imakaev).
As a result, scientists have made two main conclusions. Firstly, the human genome is "divided" into two compartments: in the first, active genes are stored, in the second, "unnecessary" parts of DNA are more tightly isolated. Moreover, there is a constant exchange of on and off genes between the two parts.
"The cell acts very cleverly by exposing active genes to a special zone where they are easily accessible to proteins and other substances," says another researcher, Job Dekker.
The second conclusion: the genome is a "fractal globule" (fractal globule). This structure allows you to:
- packing DNA is incredibly compact: the density of information in the core is about trillions of times higher than in the average computer chip;
- avoid the formation of knots or tangled fragments that would interfere with the normal operation of DNA;
- the genome is rapidly folded and decomposed during the activation and repression of genes, cell replication.
If you thin out the picture a little,
then the reasonableness of the natural approach manifests itself even more
(illustration by X. Robert Bao, Leonid A. Mirn, Maxim Imakaev).
Note that previously it was believed that DNA is packed in the form of an "equilibrium globule" (equilibrium globule). However, this configuration easily forms many nodes. The fractal globule, which was theoretically predicted about 20 years ago, has never been observed in living nature before.
The article of the authors of the work was published in Science, it was even awarded the first page of the journal. Let's see if American geneticists will receive a Nobel Prize for their "discovery" (recall that chemists who discovered the three-dimensional structure of ribosomes at the time recently became laureates of the prestigious prize).
By the way, in the future, scientists plan to see the genome in even greater detail (so far, a resolution of up to one million base pairs has been achieved).
Source: Science DailyPortal "Eternal youth" http://vechnayamolodost.ru